The 3GPP (The 3rd Generation Partnership Project), which is the standardization organization for mobile communication systems, is working on development of specifications for an EPS (Evolved Packet System) described in NPL 1 listed below as a next-generation mobile communication system. As an access system connected to the EPS, not only LTE (Long Term Evolution) but also Wireless LAN (WLAN) and WiMAX (Worldwide Interoperability for Microwave Access) are being examined.
Furthermore, the 3GPP is examining a current sharp increase in traffic caused by smartphones accessing the Internet and is assuming that LTE will not be enough to process the traffic. The 3GPP is planning to avoid concentration of traffic in LTE by switching from LTE to other access systems such as Wireless LAN and WiMAX depending on the situation.
In NPL 1, IFOM (IP Flow Mobility) is examined as a technique for avoiding concentration of traffic using a plurality of access systems and specifications thereof are developed. The IFOM is a technique that makes it possible to distribute traffic by assigning an access system for each flow. Here, the flow refers to a group of communication data having a common characteristic, and the characteristics of the communication data can be identified with, for example, a source IP address, a destination IP address, a source port number, a destination IP address, a protocol number (these five parameters are referred to as IP5), or the like.
In addition, in NPL 2, a method used by UE (User Equipment), which is a mobile communication terminal, to use an ANDSF (Access Network Discovery and Selection Function) in a procedure for switching an access system is described. The ANDSF is an apparatus having a function of, for one or a plurality of flows communicated by, or to be communicated by, the UE, selecting an access system for each flow and transmitting the selected access system to the UE as a policy of a Mobile Operator (MO).
The UE holds a policy in which an access system used for each flow is associated with each of the one or the plurality of flows communicated, or to be communicated, thereby. Upon receiving an access system from the ANDSF as an MO policy, the UE determines whether or not to apply the access system included in the MO policy, and if the MO policy is to be applied, the UE causes a UE policy to reflect the MO policy and then switches the access system used for transmitting and receiving the flow on the basis of the policy of the UE.
Here, the UE policy is set by a user in accordance with whether or not connections can be established with a plurality of access systems and billing conditions. For example, the UE policy is a policy that is related to selection of a communication path for the UE and that, for example, determines that use of a communication path through an access network realized by WLAN is given priority if cost is lower when the communication path through the access network realized by WLAN is used than when a communication path through an access network realized by LTE is used.
Therefore, the UE need not necessarily follow the MO policy transmitted from the ANDSF, and if the MO policy is not applied, the UE need not change the UE policy and, in this case, need not switch the access system. Such application is determined by the setting of the UE or setting based on the intention of the user who owns the UE.